It means IVF clinics are now free to apply for permission to carry out mitochondrial replacement therapy, which aims to prevent babies and future generations inheriting devastating genetic disorders.
Children conceived using the technique will receive a tiny amount of DNA from a third person, an egg donor, besides their mother and father.
Scientists at the University of Newcastle, which has pioneered the treatments, hope to treat 25 women a year with NHS funding.
The first patients could be given the therapy next spring, and the first babies with three genetic parents born nine months later.
The UK fertility regulator, the Human Fertilisation and Embryology Authority, said only the most serious cases would be treated. In total, up to 3,000 women are likely to qualify for the therapy.
Chairman Sally Cheshire said the “historic decision” meant parents at very high risk of having a child with life-threatening mitochondrial disease may soon have the chance of a healthy, genetically related child.
She added: “This is life-changing for those families.”
The move came after an independent panel of experts cleared away remaining safety hurdles to recommend “cautious adoption” of the treatment.
Professor Adam Balen, chairman of the British Fertility Society, which represents IVF clinics, said: “This marks a momentous and historic step and we hope families next year will begin their journey to eradicate these genetic diseases.”
Fertility doctors carrying out the treatments will aim to replace abnormal genes in the mitochondria, described as rod-like power plants in cells that generate energy.
Mitochondria only hold around 0.1% of a person’s DNA, which is always inherited from the mother and has no influence over individual characteristics such as appearance and personality.
It is separate from the DNA in the cell nucleus which house the vast majority of an individual’s genes.
But when mitochondrial DNA (mtDNA) goes wrong, the results can be catastrophic, leading to a wide range of potentially fatal conditions affecting vital organs, muscles, vision, growth and mental ability.
Despite the “cautious” approach adopted by the regulator, some critics have argued that it has acted too fast, pointing out that unforeseen problems may occur once the procedure is used to create babies. They say replacing mtDNA might have more of an impact on personal traits than has been envisaged.
But the organisation’s chief executive, Peter Thompson, dismissed any suggestion that they were being used as “human guinea pigs”.
He said: “I would whole-heartedly reject any such label that these women are guinea pigs. The key thing here is consent.
“These are women who have experienced terrible suffering that has affected them and their families. If they wish to try these new treatments that must be a decision for them.”
Newcastle upon Tyne Hospitals NHS Foundation Trust and the University of Newcastle, said they would apply for the first MRT licence “within 24 hours”.